We have a large fish pond, 20 foot long by 6 foot long, it was man made, but by not by using a premade mould, by using layers of heavy duty plastic and careful placement of rocks (I am not entirely sure, I watched my mother build it). It has some gold fish in it. It gets topped up with tank water if there's not enough rain, usually it's level is not too bad at maintaining itself. It has no chemicals. MY mother created it with the idea of mimicking nature (minus the plastic). It has some water plants growing in it.
We always have a bowl of fresh water left out for our dog, we keep it next to his food bowl. He seems to prefer drinking from the fish pond, which seems a muddy, murky comparison to fresh water. She's been doing it for years and is quite healthy.
Why would she prefer the murky pond water?